Question

I’m new using MongoDB, and I don’t know how to solve the next problem:

I have a collection of documents like this:

{
 "URL": "www.stackoverflow.com",
 "TAGS": [
         {"NAME": "question", "VOTES": 3},
         {"NAME": "answer", "VOTES": 5},
         {"NAME": "problem", "VOTES": 2}
         ]
}

First of all, I wanted all the Urls that have all the tags given in a list.
I have solved this by quering:

db.links.find( { "Tags.Name" : { $all: ["question","answers"] } } );

But this query return the whole correct document, insted of only the correct document with only the tags I have asked for.

The result I’m looking for is:

{
 "URL": "www.stackoverflow.com",
 "TAGS": [{"NAME": "question", "VOTES": 3},
         {"NAME": "answer", "VOTES": 5}]
}

and not:

{
 "URL": "www.stackoverflow.com",
 "TAGS": [{"NAME": "question", "VOTES": 3},
         {"NAME": "answer", "VOTES": 5},
         {"NAME": "problem", "VOTES": 2}]
}

Because I’ve only asked for the tags [“question”,”answers”].

I thought about using MapReduce or parsing the resultset, but I don’t know if it is the correct way of solving the problem. Maybe there is a builtin function that solve it more efficiently.

Thanks!

Answer 1

Thanks Robert. I have realized that the featured I’m looking for is not implemented at this moment. Here is the link of the issue. I hope that the MongoDB cominuty implements it in a short time. Thanks!